The present invention relates to a process for the application of solder on printed circuit boards.
In the case of a known process of this type, a guiding system consists of two vertical guiding rails each of which has a U-shaped guiding channel (German Disclosure Publication 24 11 854). The printed circuit boards are guided in these guiding channels and also are held on two narrow sides located opposite each other. The guiding rails extend from the soldering bath upward past blast nozzles from which emerge hot air jets which are directed against the surfaces of the printed circuit boards pulled out of the soldering bath. By means of these air jets, excessive solder is removed from the printed circuit board which passes by and, additionally, the solder is removed from passage holes in the printed circuit boards. In order to be able to properly hold and guide the printed circuit boards, particularly when they are exposed to the hot air jets, the width of the guiding channels is selected in such a manner that it corresponds approximately with the thickness of the printed circuit boards.
This requires a very exacting and, therefore, complex positioning of the printed circuit boards for their introduction into the guiding channels. Furthermore, printed circuit boards which are slightly curved can only be introduced with difficulty or not at all. Furthermore, an adjustment or exchange of the guiding rails becomes necessary for the processing of printed circuit boards of different widths or thicknesses. Since the printed circuit boards are softened in the hot solder bath, there is additionally the danger of damaging the printed circuit boards, which are not yet resistant to mechanical wear when leaving the soldering bath, owing to the heavy lateral guide.